Single step direct image forming electrolytic developer for photoconductographic processing



1963 D. L. JOHNSON EI'AI. 3,072,542

SINGLE STEP DIRECT IMAGE FORMING ELECTROLYTIC DEVELOPER FOR PHOTOCONDUCTOGRAPHIC PROCESSING Filed June 14, 1961 PROCESSED PHOTOGRAPH/C IMAGE OCOIVDUCT/VE LAYER LAYER SUPPORT Fig. 4

CURVE A DENSITY l 1 1 l 1 l 8 7 6 5 4 3 2 Exposure Step M/mber (0.3m; 5 Scale) 055 L. JOHNSON R YMO/VD E RE/THEL A INVENTORS ATTORNEY 8 AGE/VT United States Patent SINGLE STEP DIRECT IMAGE FORMING ELEC- TROLYTIC DEVELOPER FOR PHOTOCONDUCT- OGRAPHIC PROCESSING Dee Lynn Johnson and Raymond F. Reithel, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed June 14, 1961, Ser. No. 117,125 16 Claims. (Cl. 204-18) This invention relates to photoconductography and more particularly to a novel developer solution for single step direct image-forming photoconductographic processing.

. Photoconductography is the process of producing images by using photoelectrically sensitive materials to control the electrolytic deposition or formation of a material capable of being the image or capable of being converted to the image by other means. It forms a complete image at one time or at least a nonuniform part of this image as is distinguished from facsimile which at any one time produces only a uniform dot.

Photoconductography is described in detail in British Patent 188,030, Van Bronk, and British Patent 464,112, Goldman, modifications being described in British 789,- 309, Berchtold, and Belgian 561,403, Johnson et al.

The present invention is concerned with those processes of photoconductography in which the production of the image is brought about by a single-step direct image-forming electrolytic developer. Single-solution or single-step electrolytic developers used in this process are to be distinguished from those developers in which the electrolytic deposition or formation of a faintly visible image material is subsequently made visible by a second step, which may be chemical, electrical, or mechanical.

Single-solution electrolytic developers are those developers which will produce a useful visible image material by a single electrolytic development step and require no further treatment for image formation. The present invention pertains toprocesses of photoconductography in which the image is formed simultaneously with exposure of the photoconductive layer or in which the image is developed after exposure has terminated. (See Franz Urbach U.S. application Serial No. 64,901, filed October 25, 1960.)

The present invention also pertains to processes of photoconductography without regard for the particular method used for bringing about development of the image. Forexample, widely diverse techniques canbe employed in development to apply and distribute the developer solution over the photoconductive layer of the photocouductographic material, such as the use of an angular sweeping blade for distributing the electrolytic developer as provided by an automobile windshield wiper, a viscose sponge containing developer solution, a transfer roller covered with developer solution, a rotary brush containing developer solution, etc. Another suitable technique involves distributing the electrolytic developer over the surfaceof the print-forming layer in the area between a surface transparent electrode and the photoconductive layer.

The present invention provides an electrolytic developer which can be employed for image development in processes of photoconductography where a wide variety of photoconductive layers are employed. For example, the

photoconductive layers can comprise zinc oxide or other suitable light colored photoconductors in a suitable insulating resinous binder. The photoconductive layers can also contain sensitizing dyes or other sensitizing materials in which a higher level and range of sensitivity is obtained in a given spectral region or spectral sensitiza tion can be brought about in more than one spectral region.

Silver nitrate, thiourea-silver complexes, and thiosulfate-silver complexes have been used in electrolytic de- "velopers. These developers, however, have had various are characterized by strong oders, which are not only unpleasantto the person using the developer, but may be 'unpleasant to the person using the prints produced with them. Some of the prior art developers are characterized by reacting chemically with the zinc oxide, especially in the presence of light, after electrolytic processing and, therefore, must be thoroughly removed to avoid printout. Silver nitrate developers, for example, when left on the photoconductor surface after processing, will produce very serious printout after only 10 seconds exposure to light. Another problem with many of the prior art singlestep direct image-forming electrolytic developers has been their inability to produce images having as high a contrast and density as is desired.

It is, therefore, an object of our invention to provide a novel class of single-solution, one-step electrolytic developers for photoconductographic processing.

Another object is to provide for photoconductographic processing an electrolytic developer that produces images having higher density and higher contrast than those produced from thiosulfate-silver complex, thiourea-silver complex developers or any other one-step developers previously available.

Another object is to provide an electrolytic developer which will not react chemically with the photoconductographic surface after processing, and whose rate of printout in the presence of light is greatly reduced, thus eliminating the necessity for removing the excess unused solution by washing. A I

Still another object is to provide an electrolytic developer that is valuable for protoconductographic processing to form permanent, dense images that are stable in the presence of heat and light, as well as odorless in the final print. Still other objects will become evident from the following specification and claims.

These and other objects are accomplished by the use of the novel single-step direct image-forming electrolytic developer of our invention. According to our invention, w-aminoalkanethiol silver ion complexes are valuable developing agents for use in our single-step direct imageforming electrolytic developer for photoconductographic processing. vvThe w-aminoalkanethiols valuable for makingour silver ion complex developing agents may be described but not limited to the compounds of the followirig formula: I

amyl, a substituted alkyl group, such as 2-hydroxyethyl,,

Z-aminoethyl, Z-hydroxypropyl, 3-aminopropyl, l-methyl- Z-hydroxyethyl, l-methyl-Z-aminoethyl, Z-hydroxybutyl, l,2,3,4,5-penthydroxy-n-hexyl, 3-aminobutyl, 3-hydroxy-- l-methylpropyl, Z-amino-l-methylpropyl, methoxyethyl, ethoxyethyl, propoxyethyl, propoxypropyl, etc., an un-, saturated alkyl group, such as allyl, butenyl, etc., an,

alicyclic group, such as cyclohexyl, cyclopentyl, cyclobutyl, etc., such that R and R may be the same or different; or R and R together may represent the atoms necessary to complete with the nitrogen atom a heterocyclic group preferably having from 5 to 6 atoms in the variable reflux-ratio head. The value of n was determined by iodometric titration and confirmed by elemental analysis. In cases in which n is not an integer it represents an average value for a mixture.

TABLE I Molar n or Percent No. R R Excess Solvent aver- Yield Amino age 72 HOCIIEOI'IF H 2 to1uene-dioxane 1 (it. 5 HOCH GH2 2 do 2. 27.0 HOCHZOHz- 2 1. 35 86. H OCHzCHr- 0. 1. 67 97. (CHa)aC- 2 1 15. 0 HOOHz CI-Is)2G- 0 2. 90 66. 5 (H0OH2)2(OH O- 0 3. 43 87.0 HOCH2CH2 2 1 1 67.0 2 1. 41 j 100. 0 -O. 5 1 47. 5 0 toluene-dioxane 1. 30 8&- 0 0 v dioxane 1. 75 69. 8 NOH G -0. 5 toluene-dl0xane 1. 87' 88. 2 HOCH CHP H NCl-I CI-I 1 toluene 2. 42 6t. 0

In this reaction, ethyl Z-mercaptoethylcarbonate, when added to a refluxing mixture of 2'mole excess amine in a non-polar solvent will give 60% to 96% yields of the related Z-aminoethanethiol in which n equals 1. The preparation of ethyl Z-mercaptoethylcarbonate is described in Johnson et al. copending US. patent application, Serial No. 80,970, filed January 6', 1961. The other products of the reaction are oligomers, that is, low

molecular weight polymers in which n. equals 1, 2, 3, 4,

etc, such that the average value of n is from 1 to about 5. We have found, that it is unnecessary to separate the products of this reaction, in fact, in some cases, the use of reaction mixtures to make our electrolytic developers actually cnhanced'the density, the contrast or both density andcontrast of the electrolytically formed images. This discovery has made the invention more practical since separation of the oligomeric products is accomplished by.

fractional distillation, which for the higher boiling amines becomes difficult and expensive. Since the reaction mixture may be utilized according to our invention, we are able to use a much wider group of amine starting materials which would not be isolable by normal procedures. Furthermore, the cost of the silver complex developing agents is reduced because the yield includes all the oligomers and the work-up of the product involves only the removal of solvent and excess amine. Other methods known to the artare equally satisfactory for the preparation of specific compounds.

The followingwill further illustrate the 2-aminoethanethiols of our invention and their preparation. The 2- aminoethanethiols in Table I which follows were pre pared by the addition of ethyl Z-mercaptoethylcarbonate to a refluxing mixture of amine and solvent under an effective condenser, followed by an additional 2 hours of refluxing. Solvent and excess amine were then removed under aspirator vacuum and the product was the material remaining in the flask. The compounds for which n is an integerwere distilled through a packed column with a I is as follows:

I fl f Analysis Calculated 39'. 4 Analysis Found 39. 6

The electrolytic developer in its simplest formconsists of a water solution ofthe w-aminoalkanethiol-silver ion complex. This is formed by adding; slowly with stirring, distilled water containing; asilver compound which furnishessilver ions toadistilled water solution of the u aminoalkanethiol or mixture of w-aminoalkanethiols. Various silver compounds can be used to furnish the silver ions, for example, silver acetate, silver lactate, silver peroxide, the silver halides, and othcrsilver compounds including silver nitrate, which is the preferred compound for this purpose. The pH of the resulting complex, is adjusted where necessary by the dropwise addition of a basic material having a low ionic conductivity, such as for example Z-aminoethanol.

We have found that itis advantageous to add magnesium acetate or calcium acetate to the developer soluftion. In addition to this, acetic acidmay also be added;- When one of these acetates or the acetate and acetic acid,

are used, they are generallyincorporatedwith the distilled study'made of a typical 2-hydroxyethylaminoethanethiol compound showed that the pAg, that is, the logarithm of the reciprocal of the silver ion concentration was found to vary somewhat with variations of; pH. Increasing the pI-Ijfrom 4.7 to- 6.0produced a 0.3, log E increase in the toe speed (that is increased the density of the low density portions of; the sensitometric curve relating density to log E) and a greater increase in shoulder speed (thatis in creased the density of the upper portions of the sensitometric curve), an increase in' gamma, and an increase in density from 0.46 to 0.80. At pH values between 6 and 7, there was a further (0.3 log E) increase in toe speed; and shoulder speed with a small, increase in density. Above a pH of 7 (up to 9.0 or 10.0), there was little change in the image characteristics. The electrolytic developers are at their optimum pH values when adjusted to 7:0. Doubling the concentration of magnesium acetate pro duced no radical change in these results.

The magnesium acetate and the acetate ions in the solution act as a butter for the silver ion complexed thiourea's and as an antishorting agent. For the silver ion corn; P1 t he ns tha t ls the ma n ium re tate functions mainly as an antishorting agent at concentrations of from 3% to 5%, since at the operating pH of these developers (pH equals 7), we are above the buffering zone of this buffer which is in the range of pHs of from 5 to 5.5. It has been noticed that with some of these silver-complex developers, the magnesium acetate provides additional stability for the excess developer left on the surface of the photoconductor. This is believed to be due to a shift in equilibrium of the complex in the presence of magnesium acetate, which reduces the zinc oxide catalyzed reduction of silver ions by light.

The pAg of a typical developer made from a Z-hydroxyethylaminoethanethiol compound was varied over a wide range by the addition of silver nitrate to lower the pAg and by the addition of complexing agent to raise it. The pH and the magnesium acetate concentration was held constant... From a pAg of 7.8 (high silver ion concentration) to a pAg of 11.1 (low silver ion) there was no radi-. cal changes in developed image characteristics such as density, contrast, and speed but there was some change in image tone, background stability, and shorting. Too low a pAg produced increased shorting of the layer and decreased the stability of the background of the print to light. Too higha pAg produced bro-wn image tones. For optimum results, the pAg should be that produced by the equimolar ratio of silver ions to ligand, that is, the complexing agent.

' The concentration of our developers may be varied over wide ranges. For example, it may be varied from 0.05 to 0.2 molar. Very little change occurs in electrolytically developed image density or contrast from doubling the normal concentration. Between /2 and 1 times the normal concentration (0.1 molar there was a slight loss in density in the shoulder region of the sensitometric curve and a change in tone of the silver deposit in this region. Below A the normal concentration, there was a further loss in image density in the regions of higher photocurrents' and a solarization like effect with a change in image tone from neutral to brown being observed. The toe region of the sensitometric curve remained essentially constant throughout the concentration range from A to 2 times the normal concentration. A good concentration is from 0.05 to 0.2 molar, and there is not much to be gained by increasing the concentration above 0.1 molar in most cases.

The developer solution is applied to the photoconductographic material in any convenient way so that there is a film of, the developer solution covering the photoconductor surface to be developed. For example, the devel-. oper may be applied with a roller applicator, a sponge, a brush, poured over the photoconductor surface and then distributed by some suitable means, or the photoconductographic element may be immersed in a tray containing the developer solution so that it .covers the photoconduc-' tive surface. The developer solution may be applied to,

the photoconductor surface either before or after exposure of the element to the light image. When the developer is applied before exposure, it is possible to perform the electrolysis either during or after exposure. F or the electrolytic development, the conducting layer of .the photoconductographic element is made the cathode and an anode is then placed in contact with the developer solution so that in those areas where the photoconductor has been exposed to light and is thus made electrically conducting, there is a cathodic deposition of silver from the developer solution. The anode used in this process may take on a wide range of form, for example, it may be a stationary; rod, plate, or transparent surface film, or it may be a moving electrode which may or may not be used simultaneously to apply the developer solution, such as a roller, brush, viscose sponge, etc. When a moving electrode is used, electrolysis takes place as the electrode is moved across the photoconductor layer. Since the moving type of electrode electrolyzes only a part of the photoconductor surface at a given time, higher current densities are applied for a given total current than would be possible with 6 a fixed electrode. A wide range of voltages may beused for effecting the electrolytic development, for example, the voltage may range from 30 up to the breakdown potential of the photoconductive-layer and yield good results.-

Voltages from 60 to 80, however, are preferredfor typical photoconductographic materials.

Since the photoconductive layers act as rectifiers,.alter nating current as well as direct current can be used in the practice of our invention. Our invention is not limited as any particular mode of development. Practically all pho' toconductographic developing systems can be used to advantage with our developers. I

The single-step direct image-forming electrolytic developers of our invention and their use are further illustrated by the following specific examples, which are illustrative and are not to be considered as limiting the scope of our invention. 3

Example 1 The electrolytic developer was prepared as follows:

2.3 g. Z-aminoethanethiol hydrochloride (EvansChemetics) 10.0 g. magnesium acetate tetrahydrate 1 1.0 g. acetic acid (glacial) cc. distilled water to the above solution was added slowly, with stirring, a solution of:

3.4 g. .silver nitrate (purest grade) 100 cc. distilled water.

Z-aminoethanol was added dropwise to adjust-pH to 7.0. The pAg was 10:2.

A sheet. of commercially available dye-sensitized zinc oxide in resinous binder coated on an aluminum foil-paper laminate, was exposed 'for 5 seconds to 400 ft.-c. tungsten illumination through. a 0.3 density increment photo-' graphic stepwedge. The resulting conducting image was developed electrolytically using the above prepared developer solution contained in a viscose sponge brush electrode held at 60 volts potential, positive with respect to the photoconductive layer, and one-stroke development at a rate of 2 inches per second. A positive stepwedge pattern, resulted consisting of reduced silver and perhaps silver sulfide and silveroxide and other dense reaction productsgamma was 0.85.

Example 2 The electrolytic developer was prepared as follows:

1.25 g. 2-(Z-mercaptoethylamino)ethanol 5.0 g. magnesium acetate tetrahydrate 50 cc. distilled water H to the above solution was added slowly, with stirring, a solution of:

1.7 g. silver nitrate (purest grade) 50 cc. distilled water.

2-amino'ethanol was added dropwise to adjust pH to 7.0. The pAg was 8.5.

The dye-sensitized zinc oxide layer was exposed and developed as in Example 1 using the above prepared developer.

for the highest exposure was 0.82 and whose gamma was 1.10.

developed-with thesedevelopers A positive step-wedge pattern resulted con-; sisting of reduced silver and silver sulfide whose density 7 TABLE II mow 'QH moogoto 999999 coco a mm Example 3 The electrolytic developer was prepared in the following manner:

to the above solution was added slowly, with stirring, a solution of 3.4 g. silver nitrate (purest grade) 100 cc. distilled water;

2-aminoethanol was added dropwise to adjust pH to 6.5. The pAg was 7.70.

The dye-sensitized zinc; oxide layer was exposed and developed as in Example 1 using the above prepared developer. A positive step-wedge image pattern resulted consisting of reduced silver and some silver sulfide whose density for the highest exposure was 0.80 and whose gamma was 1.00.

Similarly, a developer solution was prepared as above in which N-methyl-2-hydroxyethylaminooligoethylene sulfide complexing agents having an average value of 1.41 for n was used. A dye-sensitized zinc oxide layer was exposed and developed as in Example 1 but using this developer. The developed image had a density of 0.80 for the highest exposure, and a gamma of 1.1-8.

Example 4 7:24 g. 8-rriercapto-6-thia-3-azaoctanol :0 g. magnesium acetate tetrahydrate 3 cc. acetic acid (glacial) 200 cc. distilled water at 80 C.

added slowly, with stirring, a solution of:

7.10 g. silver nitrate (purest grade) 200 cc. distilled water at 80- C.

The pH was adjusted to 6.0 with Z-aminoeth-anol. The

pAg was 10.5. The developer, was cooled and aged 24:

hours, then filtered before use.

Some of the above developer was poured into the electrolytic developer tray of a Model 23 Microfilm Reader-Printer (Minnesota Mining and Manufacturing Company). The zinc oxide paper in the machine was exposed for 10 seconds to 125 ft.-c. through a 1 mm. 'step width, 0.3 density. increment photographic step-wedge projected 9 X enlargement. Development was standard machine development at 80-volts potential, the zinc oxide electrode being the cathode, a silver electrode tray liner the anode for the sponge development. A positive stepwedge image pattern resulted consisting of reduced silver with some silver sulfide whose density for the highest exposure was 0.83 and whose gamma was 0.90. There were six visible density steps above a density of 0.15. As a comparison of this developer with one of those er the prior art, another sheet of the same zinc oxide coating wasexposed and developed as above using a commercially available silver nitrate-thiourea complexed developer solution. The. respltantsteprwed ge. image. had a density of 0.79 for highest exposure and a gamma of only 0.66. There were eight visible density steps above a. densityof 0.15 with this developer.

Example 5 The electrolytic developer was prepared in the follow ing manner:

2.0 g. N-(Z-hydroxyethyl)-2-aminoethy1aminooligoethylene sulfide (n=l.75) 5.0 g. magnesium acetate tetrahydrate 0.5 cc. acetic acid (glacial) 50 cc. distilled water at C.

to the above solution was added slowly, with stirring, a solution of 1.7 g. silver nitrate (purest grade) 50 cc. distilled water.

The pH was adjusted to 7.0 with Z-aminoethanol. The pAg was 7.70.

' A dye-sensitized zinc oxide layer coated on aluminum; foil-paper laminate was exposed and developed as in Example 1 using the above prepared developer solution.

The positive step-wedge image pattern consisting of reduced silver and some silver sulfide at the region of highest exposure, had a density of 0.90 and a gamma of 078.

Example 6 The electrolytic developer was prepared in the, following manner:

7.8 g. 2-hydroxyethylaminooligoethylene sulfide a -1.35): 250 cc. distilled water added slowly with stirring, a solution of:

8.5 g. silver nitrate (purest grade) 250 cc. distilled water.

Add:

25.0 g. calcium acetate monohydrate.

The

foil-paper laminate was exposed and developed as in,

Example 1 using the above prepared developer solution. The positive step-wedge image pattern consisting of reduced silver and some silver sulfide had a density of 0.85 and a gamma of 0.90. I

I Our invention is further illustrated by the accompanying drawings, FIG. I, FIG. II, FIG. III and FIG. IV.

In FIGURE I, light from light source 11 is passed through the processed photographic image 12 to expose thelight-sensitive photoconductive layer 13 that is coated on, the conductive layer 14 which is on the support 15.

In FIGURE II, the light exposed image in the lefthand portion of layer 13 has'been developed electrolytically by the passage of a direct current through the film 17 of 2-(Lmercapto-ethylamino)ethanol-silver ion complex ion complex. Curve B was obtained from a print made by electrolytically developing another sample of the same.

photoconductographic material with the same exposure in a commercial prior art developer.

A comparison of curves A and B illustrates the sharper toe, higher contrast and higher shoulder densities that characterize photoconductographic prints developed with our developers from prints developed with a typical prior art developer. Our print has 40% less density at the 7th step and 21% more density as step 1 than the corresponding print produced with the prior art developer. Curve A has a slope of about 0.78 in its straight line portion compared to a slope of about 0.5 for curve B. Thus the contrast as measured by the slope of these curves is about 56% higher for our prints than for the prior art prints.

The novel w-aminoalkanethiol-silver ion complex developers of our invention are valuable for use in electrolytic processing of photoconductographic materials in a single-step direct image-forming process. Typical developing solutions are readily prepared from 2-aminoethanethiols or mixtures of these thiols which are prepared by reacting the appropriate amine with ethyl 2-mercaptoethylca-rbonate or by other procedures known to the art. The product of this reaction can be used for preparing the silver complex merely by removal of the solvent and excess amine from the crude product. No further purification is needed unless for some reason it is desired to use a pure Z-aminoethanethiol which can be prepared from the reaction mixture by fractional distillation. The w-aminoalkanethiol-silver ion complex developers are characterized by having greatly improved stability over prior art developers. For example, these developers can be kept for 6 months and longer without noticeable change in their performance while some prior art developers have a useful storage life of only about one week. The developers are characterized by being relatively odor-free as compared to some prior art developers which have obnoxious odors. Our developers produce images having characteristically a shorter or sharper toe, a higher gamma and a higher density than the prior art developers. Because of the small dilference in density between the background and the image areas of most microfilm negatives, it is very difficult to produce a photoconductographic print using developers of the prior art without having produced an undesirable background density on the developed copy. Our developers produce prints with no background, using the poorest negatives we could find. The developed images are stable to both heat and light, and the background areas are not subject to printout as readily as are photoconductographic products developed with prior art developers. Because our developing agents are not as chemically reactive with the photoconductors when they are left on the photoconductor surface after processing even upon exposure to light, it is not necessary to wash the processed photoconductographic material. However for archival quality, washing is required. Magnesium acetate, or calcium acetate although not necessary in our developing solutions, can be used to advantage in improving image quality by reducing any tendency there may be for the photoconductor to short. Our novel developer solutions are particularly valuable, not only for their desirable and valuable characteristics, but because they can be used in a wide variety of commercially available photoconductographic developing systems.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be efiected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A single-step direct image-forming electrolytic developer for photoconductographic processing containing an aqueous solution of silver ions complexed with an a:- aminoalkanethiol.

2. A single-step direct image-forming electrolytic developer for photoconductographic processing containing an aqueous solution of silver ions complexed with at least one w-aminoalkanethiol selected from those having the formula:

wherein m represents an integer of from 2 to 4; n represents a number having an average value from 1 to about 5; R and R each represent a member selected from the class consisting of (l) a hydrogen atom, (2) an aliphatic group having from 1 to 6 carbon atoms, (3) an alicyclic group having from 3 to 6 carbon atoms, and (4) the atoms such that when R and R are connected they form with the nitrogen atom a heterocyclic ring; and R is a member selected from the class consisting of a hydrogen atom and a hydroxymethyl group.

3. An electrolytic developer of claim 2 in which the silver ions are complexed with oligome-ric mixtures of 2- aminoethanethiols in which each 2-aminoethanethiol molecule has the same value for R and the same value for R and a different value for the number n, such that the average value for n for the 2-aminoethanethiol molecules in the mixture is in the range of from more than 1 to not more than 6.

4. A single-step direct image-forming electrolytic developer for photoconductographic processing containing an aqueous solution of silver ions complexed with a 2- aminoethanethiol selected from those having the formula:

N}C zCHsS) HE CHrCHzOH wherein R represents a member selected from the class consisting of (1) a hydrogen atom, (2) a lower alkyl group having from 1 to 5 carbon atoms, (3) a hydroxyalkyl group having from 1 to 5 carbon atoms, (4) an aminoalkyl group having from 1 to 5 carbon atoms, (5) an alkoxyalkyl group having from 2 to 6 carbon atoms, (6) an unsaturated alkyl group having from 2 to 5 carbon atoms, (7) and an alicyclic group; m represents an integer of from 2 to 4; and n is a number having an average value of from 1 to about 5.

5. An electrolytic developer of claim 2 in which the silver ions are complexed with 2-(2-mercaptoethylamino) ethanol.

6. An electrolytic developer of claim 2 in which the silver ions are complexed with 2[N-(2mercaptoethyl)N- methyl]aminoethanol.

7. An electrolytic developer of claim 2 in which the silver ions are complexed with 2-hydroxyethylaminooligoethylene sulfide having an average n value of from 1 to 3.

8. An electrolytic developer of claim 2 in which the silver ions are complexed with N-(2-hydroxyethyl)-2- aminoethylaminooligoethylene sulfide.

9. A single-step direct image-forming electrolytic developer for photoconductographic processing, containing an aqueous solution of (1) silver ions complexed with an w-aminoalkanethiol and (2) a compound selected from the class consisting of calcium acetate and magnesium acetate.

10. An electrolytic developer of claim 9 in which the w-aminoalkanethiol is 2-(2-mercaptoethylamino) ethanol.

11. An electrolytic developer of claim 9 in which the w-aminoalkanethiol is 2 [N- (Z-mercaptoethyl) N-methyl] aminoethanol.

12. An electrolytic developer of claim 9 in which the w-aminoalkanethiol is 2-hydroxyethylaminooligoethylene sulfide having an average n value of from 1 to 3.

13. An electrolytic developer of claim 9 in which the w-aminoalkanethiol is N-(2-hydroxyethyl)-2-aminoethylaminooligoethylene sulfide.

14. An electrolytic developer of claim 9 in which the w-aminoalkanethiol is Z-aminoethanethiol.

15. A single-step process for electrolytically developing photoconductographic material comprising a conducting layer coated with an image exposed photoconducting layer, said electrolytic development comprising the steps of (1) applying an electrolytic developer solution selected from those of claim 1 and (2) passing an electrolyzing current through the said developer between an anode in contact with it and the image exposed areas of said photoconducting layer as the cathode, such that a corresponding silver image is deposited on the surface of said photoconducting layer.

16. A process of claim 15 in which the electrolytic developer solution contains an aqueous solution of calcium acetate and silver ions complexed with an w-aminoalkanethiol.

No references cited. 

1. A SINGLE-STEP DIRECT IMAGE-FORMING ELECTROLYTIC DEVELOPER FOR PHOTOCONDUCTOGRAPHIC PROCESSING CONTAINING AN AQUEOUS SOLUTION OF SILVER IONS COMPLEXED WITH AN WAMINOALKANETHIOL.
 15. A SINGLE-STEP PROCESS FOR ELECTROLYTICALLY DEVELOPING PHOTOCONDUCTOGRAPHIC MATERIAL COMPRISING A CONDUCTING LAYER COATED WITH AN IMAGE EXPOSED PHOTOCONDUCTING LAYER, SAID ELECTROLYTIC DEVELOPMENT COMPRISING THE STEPS OF (1) APPLYING AN ELECTROLYTIC DEVELOPER SOLUTION SELECTED FROM THOSE OF CLAIM 1 AND (2) PASSING AN ELECTROLYZING CURRENT THROUGH THE SAID DEVELOPER BETWEEN AN ANODE IN 